1. Field of Invention
The present invention relates to a bicycle and, more particularly, to a one-way transmission module arranged between a hub and a flywheel set.
2. Related Prior Art
A typical bicycle includes a frame, a fork rotationally connected to a front portion of the frame, a front wheel rotationally connected to the fork, a rear wheel rotationally connected to a rear portion of the frame, a sprocket rotationally connected to a middle portion of the frame, two cranks operatively connected to the sprocket, a flywheel set connected to the rear wheel, and a chain for operatively connecting the flywheel set to the sprocket. The rear wheel includes rim, a hub and spokes for connecting the rim to the hub. A one-way transmission mechanism is arranged between the hub and the flywheel set. Thus, the flywheel set rotates the hub, but the hub does not rotate the flywheel set.
As disclosed in Taiwanese Patent M314697, a conventional hub assembly includes a one-way transmission mechanism arranged between a hub 20 and a drum 40. The drum 40 is used to support a flywheel set. The one-way transmission mechanism includes a ring 24 fit in an opening 23 made in the hub 20, a ring 41 formed on the drum 40, and catches or pawls 42 arranged between the ring 41 and the ring 24. Each catch 42 is formed with a sharp end and an obtuse end. The ring 41 includes recesses each for receiving the obtuse end of a corresponding catch 42 so that the catches 42 can pivot relative to the ring 41. A C-clip is used to keep the catches 42 on the ring 41. The ring 24 is formed with teeth for engagement with the sharp ends of the catches 42. The ring 41 is inserted in the ring 24. When the ring 41 rotates in a first direction, the sharp ends of the catches 42 engage with some of the teeth of the ring 42 so that the ring 41 rotates the ring 24 in the first direction. As the ring 24 stops or rotates in a second direction, the sharp ends of the catches 42 rattle and slide on the teeth of the ring 42 to allow the ring 24 to rotate in the first direction relative to the ring 41. Inevitably, the teeth of the ring 24 and the catches 42 wear away against each other. In such a case, the ring 24 and the catches 42 should be removed from the hub 20 and replaced with new ones. However, it is difficult to remove the ring 24 from the hub 20. In fact, it is almost impossible to remove the ring 24 from the hub 20 without causing damage to the hub 20. Therefore, in practice, the entire hub assembly is replaced with a new hub assembly when only the ring 24 and the catches 42 are worn out.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.